Rocking the Nelson Family Tree : Pop Music: Gunnar and Matthew Nelson follow the path of their late father Ricky Nelson. They make their recording debut with ‘After the Rain.’

Forgive Gunnar Nelson if his vision of his future sounds like the premise for a family sitcom. After all, he and his twin brother Matthew are the grandsons of family sitcom pioneers Ozzie and Harriet Nelson.

“My goal is to have a house with two wings for our two separate families,” he said, looking at his identical brother. “Casa de Nelson!”

The 22-year-old twins--who do really live together, but without families--laughed off the notion of starring in their own TV show one day, though they’re completely serious about following their ancestors into show biz. But it’s their late father Ricky Nelson’s path that they’ve taken. Fronting a band simply called Nelson, the pair have launched a rock ‘n’ roll recording career with a debut album, “After the Rain,” due to be released June 26 by Geffen Records’ DGC label.

They are, though, quite mindful of the differences between Ricky’s 1957 rock ‘n’ roll start and their own 1990 version.

Basically, Ricky Nelson had “The Adventures of Ozzie & Harriet” and squealing bobby-soxers. Gunnar and Matthew have MTV and flashy Hollywood vixens.

“It’s a different time,” said Matthew, sitting with his brother in a Hollywood sound stage dressing room during a break from shooting a video for “Love and Affection,” the act’s first single. “We don’t have the luxury of a television show every week.”

The field was wide open for Ricky, who was already a teen idol when he first performed “I’m Walkin’ ” on his family’s television series. His decision to become a rocker has been attributed to his girlfriend telling him she was in love with Elvis Presley.

But Nelson, the band fronted by the twins, is just one of hundreds vying for a share of video air time. “After the Rain” is no teen-age whim, but the result of five years of teeth-cutting on the Los Angeles club circuit and work with the likes of Geffen executive John Kalodner, the rock Midas who has overseen huge successes by Aerosmith, Whitesnake and Cher.

The band’s sound, which mixes melodic hard rock and power ballads with the kind of California harmonies their dad favored with his later country-rock Stone Canyon Band, seems just the thing to turn the brothers into ‘90s teen idols, as does their distinctive long blond hair and Hollywood-hip looks.

Geffen is hosting an important, invitation-only showcase performance tonight at the Roxy to officially introduce Nelson to the industry at large. None of this guarantees that the record will ever be heard by even close to the number of people who first watched Ricky rock 33 years ago. But while not taking anything for granted, the Nelsons are confident in the strength of their genes.

“The thing that hasn’t changed is that it depends on talent, artistry and magnetism of the artist,” said Matthew, the more loquacious of the two. “We’re not just second-generation performers. It goes back four or five generations. Remember that our grandparents were with big bands before they had the TV show.”

Added Gunnar, “I’ve been playing music since I was 6 and he has been since he was 7. It was always available. Since we were tiny it was all we wanted to do.”

Still, Dec. 31, 1985, when their father died in the crash of his private plane taking him to a concert engagement, proved to be a turning point. Before that, they were ready to walk through any door open to them. After that, they wanted to make sure they deserved any success that might come their way.

A key realization came after they played on “Saturday Night Live” not long after their father’s death. The appearance had been booked before their father’s death, and they decided to go ahead with it in honor of his memory.

“I think we were the first unsigned band to play the show,” Matthew said. “But on the plane back home we looked at each other and said, ‘We weren’t ready for this.’ The major turning point was losing our dad. I was always working toward this, but I was (more determined) after that. It sure gave me a lot more desire to pick myself up and do the job. We did a lot of growing after that.”

“Mortality is a reality check,” Gunnar said. “You realize what you want to do and that life is not a dress rehearsal.”